Process of making hydrocyanic acid.



Patented July 5, 1904.

UNITED STATES PATENT OFFICE. I

WVALTHER FIELD, OF HQN NI NGEN -ON-'[HE-R1-IINE, (itElilVl A N Y.

PROCESS OF MAKING HY DROC YANIC ACID.

SPECIFICATION forming part of Letters Patent No. 764,443, dated July 5, 1904. Application filed March 23, 1903. Serial No. I49,l66. (N0 specimens.)

To all whom it may concern:

Be it known that I, WALTHER FELT), chem ist and manufacturer, a subject of the German Emperor, residing at I-Ionningen on the- Rhine, in the German Empire, have invented certain new and useful Improvements in and Relating to the Production of I-Iydrocyanic Acid, of which the following is a specification.

In the specification of my British Patent No. 24,920, dated December 6, 1901, I have described the extraction or production of hydrocyanic acid from acid, neutral, or alkaline matters containing iron-cyanogen compounds by treating such matters with mercuric chlorid and decomposing the resulting mercuric cyanid by distillation with an acid, and especial reference is made therein to the treatment of matters containing iron-cyanid compounds and having an alkaline reaction by treating the said matters with mercuric chlorid in the presence 'of an excess of a salt of magnesium, aluminium, zinc, and manganese and other metals the hydrate, oxid, or carbonate of which do not precipitate mercuric oXid from from a solution of mercuric chlorid.

I have now found in treating matters containing iron-cyanid compounds and having an alkaline reaction with solutions of the salts mentioned under my aforesaid patent that I can use other mercuric compounds such as oxid, sulfate, and the likeinstead of chlorid previous to or after adding the salts, but that the mercuric-compound solutions (if soluble mercuric salts were used) after being repeatedly used become saturated with other salts, which have had to be got rid of by crystallization,which operation is inconvenient and involves loss of mercury. By my present invention I overcome the diiliculties, as hereinafter described.

The alkaline or neutral matters containing soluble or insoluble ferric or ferrous cyanid compounds (the latter may be first oxidized) in their original condition or after having been treated with an excess of a hydrate, oxid, or carbonate of an alkali or of an alkaline earth or of magnesia are treated-with mer-- curic' oxid or other mercuric compound, addingorwithout adding the salts referred to in ing to my present invention.

with the aid of an acid.

case the solution of the mercuric salt-say of in the succeeding stage of the process accord- The excess of the mercury oxid, or, if soluble mercury salts be used, the mercury oxid precipitated by the influence of the alkaline substances, will be contained in the precipitate of ferric hydroxid and other insoluble compounds, only'the inercury combined with the cyanogen being in so-v lution. After having separated this solution from the precipitate the said precipitate is treated (after being oxidized if a ferrous-cyanid compound was used) with a salt referred to 1n my aforesaid patent, whereby the whole of the mercury oxid Will be dissolved. The

solution thereof can be used again for the decomposition of iron-'cyanld compounds, and

so, also, can the mercuric compound resulting from the mercuric-cyanid solution after the hydrocyanic acid has been distilled therefrom If such mercuriccompound solution contains too much of other salts, such as potassium or sodium salt or the like resulting from the decomposition of, the iron-cyanid compound, the mercury can be precipitated from the solution in the form of oxid or the like and be washed, and then it can be utilized as before.

It may be desirable to prevent the precipitation of the mercuric oxid or the like from the mercury-compound solution which has In this become saturated with foreign salts.

mercuric chlorid or the likein one of the salts mentioned under my aforesaid patent-- say in a solution of a haloid of magnesium, of aluminium, of zinc, or of manganese or the like-is used for decomposing the iron-cyanid compounds in the Way referred to in my said patent; but the iron cyanide of the alkaline earths are used in the decomposition instead of the alkali salts of the iron cyanids. The salts of the alkaline earths can be obtained by treating insoluble iron cyanide-such as Prussian blue, ammonium ferrocyanid, or the like with alkaline-earth compounds. The compounds of alkaline earth and ferrocyanid, in Whatever Way obtained, after the ferrous cyanids have been oxidized into ferricyiuiid are treated, either in their original condition or after adding a hydrate, oxid, or carbonate of an alkaline earth or of magnesia, (an excess thereof not being objectionable,) with one of the aforesaid salts and with a mercuric solu.

with the cyanogen of the ferricyanid, no insoluble mercury compound will be precipitated, but only ferric hydroxid and the excess of the alkaline earth or magnesium hydrate or carbonate with other insoluble impurities will be in the precipitate. After the precipitate has been separated from the mercuric solution by filtration hydrocyanic acid is disengaged from the solution by distilling with an acid which will form an insoluble salt with the alkaline earth present, such as sulfuric or phosphoric acid, the said acid combining with the alkaline earth in solution, the alkaline-earth sulfate or phosphate being precipitated and being filtered off, together with the ferric-hydroxid precipitate, at the next operation in which the mercuric solution is reused. The successive reactions are expressed by the following equations:

1 Fe.,Cy, +6Ca(OH) =3Ca FeCy +2Fe (OHM.' 2 2ca,rec ,+oaoo1,+r1,so,I

(Ja (FeCy,,) +CaSO +CaCl +H Q Although ferrocyandid compounds can be treated in the same way, it is preferable to first convert them by oxidation into ferricyanids.

Although insoluble iron cyanogen compounds can be treated in the same way, it is preferable to first render them soluble by treatment with a-hydroxid or sulfid of an alkali, of an alkaline earth, of ammonium or magnesium, or with mixtures yielding the same.

The following gives a practical example of the process when potassium ferricyanid is de composed by mercuric oxid:

Example I: Sixty-five parts of potassium ferricyanid are dissolved, say, in six hundred parts of water. To decompose this amount of ferricyanid, about one hundred and thirty parts of mercuric oxid are theoretically necessary. An excess of the mercuric compound being unimportant and in order to show how the process works with an excess of mercuric oxid, I add one hundred and fifty parts of this to the said solution and keep it boiling for about twenty minutes. The proportion of mercuric oxid used is thus: seven molecules to two molecules of the ferricyanid. The following reaction occurs:

A precipitate of ferric hydrate is formed which contains the excess of mercuric oxid.

The solution is separated from the precipitate and distilled with about seventy parts of hydrochloric acid, the strength of the acid used being unimportant and an excess being of no consequence. After about fifteen to thirty minutes boiling all hydrocyanic acid will be liberated.

(6) 6HgCy +l3KOH+18HC1:6HgQl +6KCl+12HCN+6H Q The solution contains mercuric chlorid and potassium chlorid. It may be used again for further decompositions of alkaline ferricyanid:

1 2K FeCy.,+6HgCl,+6KC1-H$KOH= 6H o +1sxo1+re ion)... The more the mercuric solution is used the more alkali chlorid it contains. From time to time, therefore, the mercuric compound must be separated from the alkali chlorid, which I may do by precipitating the mercury by an alkaline compound:

a 6HgOl +18KC1+6Ca(OH) :6HgO+18KCl+6CaCl +GH O.

The precipitate of the first treatment, (reaction No. 5,) containing ferric hydroxid with about twenty parts of mercuric oxid, is treated with a salt of magnesia, alumina, zinc, or manganese or others which are decomposed by mercuric oxid. I take an excess of magnesium chloridsay forty parts-whichI dissolve in about two hundred parts of water and heat the precipitate with this solution. All the mercuric oxid will be dissolved, and the hotter the solution the quicker the reaction will be:

The mercuric oxid precipitated in accordance with reaction No. 8 may be used again to decompose iron cyanids, or I may dissolve it by treatment with magnesium chlorid in the same way as shown in reaction No.9. In this case I mix the two mercuric-magnesiumchlorid solutions and use them to decompose an alkaline-earth ferricyanid. The following Example II shows that the mercuric compound is kept nearly free from other salts if I work in this way:

Example II: Fifty-five parts of calcium ferricyanid are dissolved in about six hundred parts of water. The solution may be more or less concentrated, the result being the same. If the solution is of alkaline reaction, I add so much of one of the salts mentioned as is necessary to neutralize the solution in order to avoid the precipitation of mercuric oxid if the mercuric-chlorid solution is added. To this solution I add the mercuricchlorid magnesium chlorid solution resulting from Example I. This contains one hundred and fifty parts of mercuric oxid in form of mercuric chlorid. The proportions, therefore, are the same as in Example I. Both solutions that of ferricyanid and that of mercuric chlorid and magnesium chloridare heated, preferably, to the boiling-point before being mixed. If the ferrieyanid solution has no alkaline reaction, I may add an oxid, hydroxid, or carbonate of an alkali, alkaline earth, or of magnesium before or after the solutions are mixed. 1 take so much of calcium carbonate (chalk) as is necessary to precipitate the whole of theiron. Thirty parts of it are sufiicient. Using more chalk will not alter the result. After having mixed the solutions and added the chalk five or ten minutes boiling wil1complete the decomposition. The solution is separated from the precipitate, which contains only ferric hydroxid and the excess of chalk used. The solution is distilled with about sixty parts of sulfuric acid in order to render the calcium insoluble. After the solution is free from hydrocyanic acid it is preferably neutralized by, an oxidof an alkaline earth and may be used again without being separated from the insoluble calcium sulfate, this being filtered ofli, together with the ferric hydroxid, after the next operation. The successive reactions are expressed by thefollowing equations:

10 ca Feo ,+m o1,+1cM eu+3ea(1o,+arI,o=

GHg'CYrl-HgCh-I-l(iMgCl-;+UC:LUl +Fe (O[T),,+3CQ

11 (JHgCyl-HgCl -|-16MgGl -{-GCaCl -l-GH SO z m c1,+1t1v1 c1,- -ueaso. +12HON.

(10a) Ca (FeCy,,),-}-THgC1 --{-1U1V[g()1 -|-6CaSO.,-|-3CaCO 31-1 0:(iilgCy -f-flgcl -Hfilwgcl +(5CaC1 (iCaSO -l-Fe (OH) +00...

The underlined compounds are the insoluble ones. 1

I claim as my invention 1. The process of making hydrocyanic acid by aid of mercuric compounds from matters containing iron cyanids, which consists in treating them with alkaline substances which will precipitate ferric hydroxid from ferric salts, and with mercuric compounds together with a salt of a metal the hydrate, oxid and carbonate of which do not precipitate mercuric compounds from mercuriesolutions,

separating the mercuric-cyanid solution thus formed, from the precip tate and decomposmg the mercurlc'cyanid by distillation with acid.

2. The process of making hydrocyanic acid by aid of mercuric compounds from matters containing iron cyanids, which process consists in treating insolublematters with alkaline substances to dissolve the iron cyanid, and

treating them with mercuric compounds together with a salt of a metal the hydrate oxid and carbonate of which do not precipitate mercuric compounds from mercuric solutions, separating the mercuric-cyanid solution thus formed fromthe precipitate and decomposing the mercuric cyanidby distillation with acid.

3. The process of making hydrocyanic acid by aid of mercuric compounds from matters containing iron cyanids, which process consists.in the preliminary conversion of the iron cyanids into alkaline-earthiron-cyanid com: pounds, treating with mercuric compounds to gether with a salt of a metal, the hydrate okid and carbonate of which do not precipitate mercuric compounds from mercuric solutions, separating the mercuric-cyanid solution thus formed from the precipitate and decomposing the mercuric cyanid by distillation with an acid, which forms an lnsoluble salt w1th the alkaline earth of the alkaline-earth-ironcyamd compound. V

4. The process of making hydrocyanic acid by aid of mercuric compounds from, matters containing iron cyanid s, which process consists in the preliminary conversion of ferrouscyanid compounds into ferric cyan compounds by oxidizing means treating with mercuric compounds together with a salt of a metal the hydrate oxid and carbonate of which do not precipitate mercuric compounds from mer- In testimony whereof I affix my signature in presence of two witnesses.

WVAL'JTHER FELD. NVitnesses:

W. FRIIRR VON LYNDKER, CARL Semurr'r. 

